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Biomedical subjects

M A Callahan

Publications and source records attributed to M A Callahan.

At least 19 recordsLinked to original sources
PubMed1998

Functional interaction of human immunodeficiency virus type 1 Vpu and Gag with a novel member of the tetratricopeptide repeat protein family.

Viral protein U (Vpu) is a protein encoded by human immunodeficiency virus type 1 (HIV-1) that promotes the degradation of the virus receptor, CD4, and enhances the release of virus particles from cells. We isolated a cDNA that encodes a novel cellular protein that interacts with Vpu in vitro, in vivo, and in yeast cells. This Vpu-binding protein (UBP) has a molecular mass of 41 kDa and is expressed ubiquitously in human tissues at the RNA level. UBP is a novel member of the tetratricopeptide repeat (TPR) protein family containing four copies of the 34-amino-acid TPR motif. Other proteins that contain TPR motifs include members of the immunophilin superfamily, organelle-targeting proteins, and a protein phosphatase. UBP also interacts directly with HIV-1 Gag protein, the principal structural component of the viral capsid. However, when Vpu and Gag are coexpressed, stable interaction between UBP and Gag is diminished. Furthermore, overexpression of UBP in virus-producing cells resulted in a significant reduction in HIV-1 virion release. Taken together, these data indicate that UBP plays a role in Vpu-mediated enhancement of particle release.

Amino Acid Sequence↗
PubMed1995

Estimating exposure and dose to characterize health risks: the role of human tissue monitoring in exposure assessment.

Exposure assessment is an integral part of health risk characterization. Exposure assessments typically address three critical aspects of exposure: the number of people exposed to the environmental toxicant, at specific concentrations, for the time period of interest; the resulting dose; and the relative contribution of important sources and pathways to exposure/dose. Because historically both "point-of-contact" measurements and information about dose and related pharmacokinetic processes have been lacking, exposure assessments have had to rely on construction of "scenarios" to estimate exposure and dose. This could change, however, as advances in development of biologic markers of exposure and dose make it possible to measure and interpret toxicant concentrations in accessible human tissues. The increasing availability of "biomarkers," coupled with improvements in pharmacokinetic understanding, present opportunities to estimate ("reconstruct") exposure from measurements of dose and knowledge of intake and uptake parameters. Human tissue monitoring, however, is not a substitute for more traditional methods of measuring exposure, but rather a complementary approach. A combination of exposure measurements and dose measurements provides the most credible scientific basis for exposure assessment.

Biomarkers↗
PubMed1989

Mohs micrographic surgery for periorbital skin cancer.

The authors have illustrated the use of the Mohs technique on periorbital skin cancer. The indications for the technique are documented for eyelid and canthal neoplasia, and the case histories illustrate the potential danger of skin cancer in this area. It is the well balanced team of micrographic surgeons and reconstructive surgeons that will give the patient the best result.

Adult↗
PubMed1983

Prevention of blindness after blepharoplasty.

As reported in the medical literature, approximately 68 patients have been blinded by complications of the blepharoplasty procedure. All cases have been associated with intraoperative or postoperative orbital hemorrhage. Those factors which will help blepharoplasty surgeons reduce the occurrence of orbital hemorrhage and subsequent blindness are reviewed.

Adipose Tissue↗
PubMed1981

Surgically mismanaged ptosis associated with double elevator palsy.

The primary goal in mismanaged as well as untreated cases of combined double elevator muscle palsy and ptosis is alleviation of the paretic ocular motor imbalance to correct pseudoptosis, followed, if necessary, by levator resection to correct any residual true ptosis component. The great hypotropia often found in double elevator muscle palsy should be corrected, preferably by a muscle transposition procedure combined, in certain cases, with inferior rectus muscle recession if the inferior rectus muscle has contracted. Only in young patients can these two surgical procedures be safely combined, particularly if it is desirable to decrease the number of general anesthetics that the patient must take. Only after proper management of the paretic strabismus should the levator be resected, because, in certain cases, extraocular muscle surgery will completely abolish the upper lid ptosis.

Adult↗
PubMed1980

Mustardé flap lower lid reconstruction after malignancy.

The Mustardé rotational cheek flap has been used to reconstruct the lower eyelids of 55 patients since 1964. Results and complications were well-documented with preoperative and postoperative photographs, and the patients have been followed from one to 14 years with a mean age follow-up of seven years. The most frequent complications were downward contraction and sagging of the flap and ectropion of the lid margin. To prevent them, the zygomatico-cheek flap must be carefully designed, rotated, and sutured as high as possible so that immediately postoperatively, the palpebral fissure is only a narrow slit. The flap's lining should be of nasal septal mucosa and cartilage joined with permanent sutures to the medial and lateral canthal tendons.

Adult↗
PubMed1979

"Congenital" hematic cyst of the orbit.

A case of true hematic cyst of the orbit in a 10-year-old girl, apparently resulting from birth trauma, is presented. Ultrasonic and clinical features believed to aid the examiner in correctly diagnosing such a lesion are presented. While apparently unique among reported cases, "congenital" hematic cysts of the orbit undoubtedly occur occasionally and the possibility of this entity should be considered in appropriate circumstances.

Birth Injuries↗